The report reviewed previous research studies into the effectiveness of assisted reproduction therapy.

Women had their stress levels assessed in the 14 studies examined before beginning treatment and then underwent a single cycle of assisted reproductive therapy.

Stress levels were measured using recognized psychological techniques and included traits like anxiety, tension and depression.

Researchers in each study looked at whether women who were stressed before the start of their treatment were any more or less likely to become pregnant.

The results showed that stress had no impact on whether a woman became pregnant or not.

Professor Jacky Bolvin, the lead researcher from Cardiff University, told BBC that it was a "common myth" that women who were stressed would impede the effectiveness of fertility treatment.

She commented: "There are a lot of myths around how people get pregnant.

"Women having fertility treatment who do not get pregnant early on often blame themselves for getting too stressed out and the longer they remain not pregnant the more stressed they get. This just reinforces the myth."

However, she did feel it was important that women did not ignore the stress that they were feeling: "Fertility treatments are stressful in themselves. Women should not ignore feeling stressed - because apart from anything it could mean that they do not persist with treatment."

About one third of couples end assisted reproductive treatments early, because of the stress involved in undergoing treatment.

Clare Lewis-Jones, chief executive of the charity Infertility Network U.K., told BBC that the report was encouraging, but agreed it was important not to ignore stress.

"Whilst stress may not impact on the success of treatment, the need for patients to receive support and understanding should not be ignored."

"Clinics should ensure that they make every effort to care for their patients not only in terms of the best possible treatment but also to support their emotional and practical needs."

The results of this study are reported in the British Medical Journal.